This invention relates to a semiconductor integrated circuit device and a technique for fabrication thereof, particularly to a technique which is effective when applied to an interconnection-forming technique for a semiconductor circuit.
As an interconnection forming process for a semiconductor integrated circuit, there is a process, for example, called a Damascene process. In this process, a buried interconnection is formed in an interconnection-forming groove by making an interconnection-forming groove in an insulating film, depositing an interconnection-forming conductor film all over the surface of the semiconductor substrate and then removing the conductor film at portions other than the groove by a chemical mechanical polishing method (CMP). This process is under investigation as a process for forming a buried interconnection composed of a copper base (copper or copper alloy) conductor material, on which it has been difficult to perform minute etching.
There also exists a Dual-Damascene process, which is an application of the above-described damascene process, in which a buried interconnection is formed in an interconnection-forming groove and a plug is formed in a connecting hole by making, in an insulating film, an interconnection-forming groove and a hole for connecting with a lower interconnection, depositing an interconnection-forming conductor film all over the surface of a semiconductor substrate and then removing the conductor film at portions other than the grooves by CMP Particularly, in a semiconductor integrated circuit device having a multi-layered structure, the above process makes it possible to reduce the number of steps and, therefore, to decrease the interconnection cost.
The above-mentioned interconnection forming technique is described, for example, in Japanese Patent Application Laid-Open No HEI 8-78410, “1996 Symp. VLSI Tech. Digest pp.48-49”, “Electron materials, March issue, 22-27 (1996)”, Japanese Patent Application Laid-Open No. HEI 8-148560 or “IBM. J. Res. Develop. Vol. 39(4), 419-435 (July, 1995)”.